P0404: EGR A Control Circuit Range/Performance

Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx. P0404 is the function check of the valve drive: on valves with a position sensor the module compares commanded and actual position, and a persistent deviation means the valve sticks, is coked or its drive is too weak (GM diesel 2018 above 10 %, GM petrol 2004 above 15 %, both MIL after two trips). Ford calls it control stuck. Saab's V6 diesel deviates and uses P0404 for a short to positive. EGR control is then switched off and the valve de-energised.

Symptoms

• Check engine light on
• EGR deactivated
• Rough idle or jerking if the valve hangs open
• Diesel: possibly reduced power

Most likely causes

• Valve coked or stiff
• Valve drive (motor, gear) worn
• Position sensor in the valve inaccurate
• Supply voltage too low or ground fault

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the connector and any vacuum hoses
2. Compare the reading with other engine data while varying the engine speed.
3. Use live data to compare the commanded opening with the actual opening
4. Clean the valve and passages if they are clogged with carbon
5. Test the actuator with the scanner
6. Replace the valve if it still does not follow the command after cleaning

Good to know

• Repair difficulty: medium
• It can trigger limp mode.
• It affects emissions.

What each character of P0404 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 4: Emissions
• 04: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0404?

Drive gently and schedule the inspection soon. You may notice jerking, a lack of power, or stalling if the valve stays partly open.

What causes code P0404?

The most common causes are: valve coked or stiff; valve drive (motor, gear) worn; position sensor in the valve inaccurate.

Related codes

• P0403EGR A Control Circuit/Open
• P042EEGR A Control Stuck Open
• P0401EGR A Flow Insufficient Detected
• P0405EGR Sensor A Circuit Low

Sources

• gsi.ext.gm.com: 18OBDG04 Engine Diagnostics
• gsi.ext.gm.com: 2004file4
• fordservicecontent.com: OBD Operations Summary Gasoline 2020 2023
• saabwisonline.com: p0404

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.